Polyetherimide (hereinafter referred to as PEI) based resin is superior in mechanical properties, fire retardancy, heat resistance, fuming resistance and the like, so polyetherimide-based resin is used as super engineering plastics of films, fibers or injection molding materials for electric parts, automotive parts, etc.
Recently, in the fields of aircraft, ships, automobiles and the like, a method of using a hook-and-loop fastener as a means for covering the inner surface by attaching an interior material such as a ceiling material, a wall material, a floor material or the like to a skeletal structure such as a fuselage, a hull or a car body has been proposed. In addition, a method of using a hook-and-loop fastener as a means for fixing a skin material covering a cushion material to the surface of the cushion material has been proposed also for the seat sheet used in these fields.
In addition, extremely high degree of fire retardancy and low fuming property are required for hook-and-loop fasteners used in such fields, particularly in the field of aircraft, and the PEI-based resins are expected as few resins capable of meeting these demands.
For example, the following Patent Literature 1 describes that a cloth obtained by weaving a PEI-based fiber is used for a hook-and-loop fastener. However, since the hook fastener obtained by weaving the PEI-based fiber cannot obtain a sufficient engaging force because the hook-shaped engaging element easily extends, a hook fastener capable of obtaining a higher engaging force is required.
Hook fasteners are roughly divided into two types: woven hook fasteners and molded hook fasteners. Further, the molded hook fasteners are largely classified into one manufactured by an injection molding method and one manufactured by an extrusion molding method.
The woven hook fastener is prepared by weaving a monofilament fiber for engaging element into a base fabric, projecting a large number of the monofilament fibers on the surface of the base cloth in a loop shape, fixing the loop shape under heat treatment, and then cutting one leg of the loop into a hook-shaped engaging element or melting a tip of the loop to form a mushroom-like engaging element.
On the other hand, among the means for obtaining a hook fastener, the injection molding method is a method in which a molten resin is allowed to flow over the surface of a mold having a large number of hook-shaped or Y-shaped cavities and then solidified, after which a resin sheet is peeled off from the mold to obtain a hook-and-loop fastener. In the other extrusion molding method, a resin is extruded from a nozzle having a slit having the same cross-sectional shape as the substrate and the engaging element present on the surface of the substrate into the form of a tape having a substrate and projections for the engaging element present on the surface of the substrate. Then, a cut is made in the projection for the engaging element in the tape width direction, and then the cut is expanded so as to widen the cut line to make the projections into a row of the engaging elements.
Among these hook fasteners, in the case of a woven hook fastener, a monofilament is woven into a base fabric, so that a big problem with respect to the moldability of the resin does not arise. However, in the case of the molded hook fastener, there is a disadvantage of problems such that it is difficult to flow a resin faithfully into a narrow cavity; engaging elements are easy to be cut when forcibly pulling out from the cavity after solidifying the resin; when pulled out, the engaging element is stretched and does not become a hook shape; it is difficult to discharge the resin faithfully to the shape of a thin slit for engaging elements; and furthermore, the projection is broken at the time of cutting or the tape-shaped material is easily cut at the time of stretching. Therefore, the moldability of the resin is extremely important.
The present inventors have found that when a molded hook fastener is manufactured by an injection molding method or an extrusion molding method of a PEI-based resin as a material, a molded hook fastener made of a PEI-based resin was manufactured with an expectation such that the resulting molded hook fastener is higher than the woven hook fastener in the engaging force.
However, when a molded hook fastener is manufactured using a PEI-based resin as a molding material, a molded hook fastener having a desired engaging force could not be obtained because the resulting molded hook fastener did not face a direction such that the male engaging element can engage with the engaging partner, or there were many engaging elements which were cut in the middle of the engaging element.
It is conceivable to improve the moldability by mixing a resin having excellent moldability with a PEI-based resin as a means for solving the low engaging force caused by poor moldability of such PEI-based resin. However, when most of the resin is blended in an amount necessary for improving moldability with the PEI-based resin, the fire retardancy and low fuming property of the PEI-based resin of the resulting molded hook-and-loop fastener has remarkably disappeared, so that necessary fire retardancy or low fuming property could not be satisfied at all. In addition, among the resins, there are also many cases where further deterioration of the moldability of the PEI-based resin occurred by mixing.